You can get 38 RIM fire ammunition at your local gun shop. I would recommend visiting your local firearms expert to see what they would reccommend for your weapon.
Online; Gunbroker and Luckygunner may be able to direct you to a brick-and-mortar store near you.
The difference is explained in the name. A rim fire rifle uses ammunition where the hammer strikes the rim of the bullet. In a center fire rifle, the hammer hits the the center of the bullet. Rim fire ammunition is usually small, like a .22, and center fire ammo is generally larger.
A firearm chambered to fire 38 special ammunition
NEVER FIRE OR ATTEMPT TO FIRE AMMUNITION IN A WEAPON NOT DESIGNED FOR THAT AMMUNITION!!!!!!!!!!!!!!!!!!!!!!!!!!! Danger,danger, danger
Try Old Western Scrounger
Never fire ammunition in your weapon that it is not chambered for.
The location of the primer. In the rim, or at the rear center of the cartridge case. Most centerfire cartridges can be reloaded, most rimfire cannot be.
Position of the primer- on the rim or rear center of cartridge case. In general, rimfire ammo is less powerful and cannot be reloaded.
Center fire cartridges have a primer at the rear center. Rimfire cartridges have priming compound in a fold all the way around the cartridge rim. The firing pin pinches a point on the rim, making the cartridge fire. They are not considered to be reloadable.
Although it can be done, DO NOT !! Never fire ammunition in a weapon that it is not chambered for.
NEVER FIRE AMMUNITION IN A WEAPON IT IS NOT CHAMBERED FOR!!!!!!!!!!!!!!!!! No, No, NO
NEVER FIRE AMMUNITION IN A WEAPON NOT DESIGNED FOR IT!!!!!!!!!!!!!!!!!! If you have ANY doubts, have it examined by a competent gunsmith. <><><> No- two different cartridges.